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sree harshini Grade: 9

a body is throw upin a lift with a velocity 'u' relativeto the lift. it returns to the floor of lift in time t. then the upward acceleration to the lift is

7 years ago

Answers : (1)

Puneet Mittal AskiitiansExpert-IITD
22 Points

Hi Sree,

Let the upward accelaration of the lift is a' .

Now for an observer in the lift , a pseudo force ma' will be acting on the body ( of mass m ) in the direction opposite to the direction of motion of accelaration of lift.

Thus forces acting on body will be : ma' downwards and mg downwards.

Thus Net force = MA = ma' + mg where A is net accelaration of the body. A is  downwards.

Now, using equation of motion,

0 = ut + 1/2( - A )t2

1/2At2  = ut

At = 2u

A = 2u/t

Now a' + g = A

a' + g = 2u/t

Thus a' = 2u/t - g  is upward accelaration of the lift.

Please feel free to ask as many questions as you want.


7 years ago
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